Process control in warping-2

Efficiency of Warping Department

The following will calculate the efficiency of a warping machine:

Let Speed in m/min= 300
Set length (m) = 18000
Yarn length on cone/cheese (m)= 54000
Number of Ends/beam= 500
end breaks/400 ends/ 1000 m = 3
Time to mend a warp break (seconds) = 35
Time to change a beam (seconds) = 500
Time to change a creel (seconds) = 3000
Time loss due to miscellaneous causes/1000 m (seconds)= 25

Calculation

Running time R (s) = 1000x60/300 = 200
R is the uninterrupted running time in meters
Breaks/running ends in beam/1000 m = 3x500/400 = 3.75
Stoppage time /1000 m
(a) to mend breaks (s)= 3.75x35 =131 s
(b) to change a beam (seconds) = 500x1000/18000 = 28 s
(c) to change a creel = 3000x1000/54000 = 56 sec
(d) Miscellaneous time = 25 seconds

Therefore, S, the total stoppage time per 1000 meters (s)= 131+28+56+25 = 240 s

Therefore total efficiency = Rx100/(R+S)= 200x100(200+240) = 45.5 %

Expected Production per shift of 8 hours (m) = (300x60x8x45.5)/100 = 65,500 m

Causes of Low efficiency or Low productivity

1. Increase in End breakage rate

The machine efficiency at warping is highly sensitive to the end breakage rate

2. Improper utilisation of magazine creel

If the creel boy does not keep the magazine creel ready to be used by the time the package in the running creel are over, the efficiency will fall.

3. Reduction in Average Set-length

Lower set lengths reduce the machine efficeincy at warping

4. Number of Tenters per Machine

The number of tenters per machine determine the time to mend an end break. This is because by the time the warper finds a broken end on the beam, the creel boy brings the other end of the broken yarn from the creel

5. Stops due to Machine Breakdown, shortage of cones etc.

If the stops due to machine breakdown, shortage of empty beams or cones/cheeses etc. are high, the actual efficiency of the machine will be lower than calculated.

Process Control in Warping-1

Process Control in Warping

Warping is the process of winding together on a beam a specified number of warp ends from Creel. The creel is a convenient rack for holding spools, cones or cheeses while the yarn is withdrawn to the warp beam.

The following are the process control parameters in a warping department:

1. Minimising End breaks.
2. Quality of warping beam
3. Control of productivity

Importance of Minimising end breaks:

The stoppage of the machine due to an end break is likely to deteriorate the quality of the beam due to three reasons:

1. The rubbing of the beam by the drum which stops abruptly.
2. Owing to the difficulty in finding the broken end, there is a possibility of incorrect mending. It may lead to lappers during sizing.
3. There is some loss in the extensibility of broken end when the machine is stopped, it increases the probability of breakage in weaving and sizing.

The following points should be noted to improve the quality of warping beams:

1. condition of beam flanges:

If the beam flanges are damaged, the unwinding of yarn near the flanges will not be satisfactory. This will cause difficulties in sizing and weaving.

2. Stop Motions and Breaks:

Proper stopping of the warping machine after an end break ensures that the broken end on the beam can be traced easily.

3. condition of the driving drum:

On most warping machines the beam is driven by fricitonal contact with the driving drum. In order to get a package of the correct density, the pressure between the drum and the warper's beam has to be kept at fairly high level.

4. Barrel Diameter of the Beam

Beams of small barrel diameter give rise to high unwinding tension at sizing, particularly when the beam is about to become empty.

5. Cuts in Accessories in the path of yarn

Drop pins of stop motion, guide rollers, reed denting etc. should bot have any grooves.

6. Creel Fans

Fluff accumulated on the machine, particularly at thread guides, causes tension variations in the yarn. This fluff can pass on to the beam.

7. Length Measuring Motion

The length measuring motion should be accurate, otherwise estimation of beam count would be wrong and subsequently will give incorrect values of size percent which is commonly determined from the weights of yarns on the warper's and the size beams.

8. Density of the Beam

The beam should be firm, inadequate pressure between the beam and the drum causes soft beam. Adequate pressure should be maintained by making suitable mechanical adjustments.

Control of Productivity

The productivity at warping depends upon the machine efficiency and machine speeds. The speed is governed by the mechanical condition of the machine and its design. Machine efficiency depends on several factors, such as the breakage rate, the time taken to mend the machine stop, set length, length of yarn on supply package etc.

FAQ in cotton Spinning-11

Q: Why cotton system of spinning is called so ?
Ans: Because it was initially developed for spinning cotton fibres.

Q: How fiber length affects spinning ?
Ans: A longer fiber can be spun to a finer counts and gives a better spinning performance. In general, the longer the fiber, the higher the yarn tenacity. Too long a fiber gives processing problems specially in carding. Productivity also increases because the yarn spun from a longer fiber needs a lower twist.

Q: What should be the min. number of fibres in the yarn cross section for better spinning performance.
Ans: It should be around 85 for 38 mm and 68 for 51mm fibre

Q: How finer fiber affects spinning performance.
Ans: A fiber fiber can allow spinning of finer yarns. It also leads to more even yarns. Also low twist is required because of greater interfiber friction. However it can lead to excessive neps at carding.

Q: How finer fiber affects the fabric.
Ans: Fabrics produced from finer fibers drape better. They also have a soft "sheen". It usually produces softer fabrics.

Q: What is the formula to calculate the number of fibres in a yarn cross section.
Ans: N = (5315/fiber denier)/ yarn count (Ne)

Q: What is the min fiber strength needed for spinning ?
Ans:0.6 to 0.7 grams/denier

Q: What is crimp. How does it affect spinning.
Ans: It is defined as the weaviness of a fiber. It increases the interfiber friction which helps in spinning process. It also produces yarns and fabrics haveing a greater bulk and a softer feel.

Q: How crimp is measured.
Ans: Crimp is measured in arcs/inch

Q: What will happen if crimp is lower? If crimp is higher ?
Ans: A lower level of crimp than recommended can lead to problems such as  lap licking, higher cylinder loading, card web breaking and roller lapping. A higher level of crimp will lead to excessive neps.

Dyeing Hints

This site talks about very practical dyeing hints. Some of which are "animals are acidic and botanicals are basic", how to measure mordants and dyestuff, besides dyeing terminology.